When it comes to extracting callories from food, what percentage of the callories in different food callorie sources (fat, carbohydrates, proteins) is digested and not just passed through the gut unused. Do these efficiency percentages change much between different people, or in special cases?
Does food labelling take into account the standard digestive efficiency (or is it close enough to 100% that stating the absolute amount of callories in the food is sufficient). I believe fiber has callorific content (in that it can be burnt) but is not included in food callori counts because fiber is not digested at all.
Depends on the food, and food labeling doesn’t take this into account.
IANA doctor, but I have two points to make:
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I have heard that the reason fats are to be avoided (other than energy density) is that to convert carbohydrates and proteins to fat for storage, your body uses approx 10% of the caloric value. In other words, 100 fat calories gets deposited directly, while 100 protein calories gets deposited as 90.
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As for efficiencies, I have always thought this is what people mean when they say “Oh, I stay thin even though I eat like a horse because I have a good metabolism.” This is a bit incorrect, because if I eat 10 snickers bars and don’t get anything stored, and you eat 10 snickers bars and gain two pounds, I’m the one with the ‘good’ metabolism, when in effect I am the one with the inefficient metabolism.
Digestion can be defined as the process of breaking large food molecules down to their most basic components. This means that starches and complex sugars are broken down to simple sugars (and those eventually to glucose); fats are broken down to fatty acids; and proteins are broken down to amino acids.
For the most part, normal digestion is extremely efficient at this. The human body produces a gigantic number of enzymes specifically designed for the purpose.
There are exceptions. Fiber is a general term for various types of cellulose, but it all can be considered to be indigestible. The body is adapted for this, and some fiber is in fact a dietary necessity to keep the intestines functioning properly.
The majority of adults in the world no longer manufacture the lactase enzyme that digests lactose. This can create symptoms if dairy products are eaten, but otherwise makes no difference.
A variety of diseases and other conditions can result in undigested food molecules, but these are abnormalities rather than the norm.
So the dietary efficiency of food is indeed very close to the standard of 4 calories per gram of protein or sugar and 9 calories per gram of fat.
Storage is a completely different issue than digestion. The number of calories burned per day will determine what is stored in the body and how it is stored. But this is entirely post-digestion.
Thanks, I susspected efficiency was very high. But this lead me to the TMI thought.
Often food does not seem to change much during its journey through the digestive system, such things as mushroom slices, sweetcorn, raisins, beans, can leave the digestive system apparently (by sight anyway) unchanged. Has the calorific contents of these things actually been efficiently extracted, or are they really undigested?
Also on a personal level I have had my gall blader removed. Does this greatly effect the efficiency with which my body absorbs energy from fat contents of foods? Since bile is released constantly into my system, and not just when it is required, and bile being important in digesting fats?
If you see even slightly recognizable food leaving your body - by any route :eek: - then it is undigested. The less recognizable, the more digestion has taken place. It’s a continuum so there’s no general answer about absorption.
I understand that after gall bladder removal a very low-fat diet is recommended because fats cannot be digested as efficiently. Not my area of expertise, though, so one of the real doctors should answer this.
And on the corn note, what you are probably seeing are the undigested outter casings of the corn, but the insides are empty, well, empty of usable food contents… probably full of SOMETHING, but I’ll leave it to you to guess what.
Really? What about undigested food like corn kernels?
Nevermind… should have previewed. :smack:
Do a scientific experiment. Try passing it through again, monitor your caloric intake, and see if you can gain additional calories that way.
I’d rather just hear the results of a nutrition scientist’s experiments. After all it wouldn’t be right to just waltz in on another’s speciality research area without the propper background knowledge 